1. Field of the Invention
The present invention relates to a wireless power supply method for supplying electric power wirelessly by electromagnetic waves (microwaves).
2. Description of the Related Art
In recent years, a technology that supplies the electric power by electromagnetic waves and supplies the electric power wirelessly has been developed. As an example of a wireless power supply technology by the electromagnetic waves, there is a method that uses the binding or resonance of the magnetic field in a short distance equal to or less than several meters, such as electromagnetic induction or magnetic resonance using the electromagnetic waves with a frequency bandwidth from several 100 KHz to several MHz.
In addition, there is a system that uses the microwave as a wireless power transmission method in a case where the distance from a power transmission device to a power reception device is long. It is possible to transmit the electric power to a remote power reception device by using a microwave beam from several 100 MHz to several GHz. As an example of such a wireless power transmission system, there is a space solar power generation system in which a satellite on which solar panels are mounted is launched above the equator, and the electric power generated by solar light is transmitted to the power reception device on the ground. In addition, there is a system or the like that transmits the electric power to a power reception device installed on a remote island.
There are fewer restrictions on a transmission distance in a power transmission method by the microwave compared to other methods. Therefore, a system for supplying power to an object that moves (moving object), such as an electric car and a robot has been proposed.
However, in the power supply system, a relative position is changed between the power transmission device and the power reception device according to the movement of the moving object that is a power supply target. Therefore, there is a problem that a microwave beam generated from the power transmission device cannot be properly transmitted to the power reception device of the moving object. Accordingly, there are problems of fluctuation of power transmission efficiency of the power supply system, safety on the electromagnetic waves that leak to an outside of the power supply system, influence of the leaking electromagnetic waves on other equipment, or interference of the leaking electromagnetic waves with other electric waves.
For such problems, a technique that transmits a microwave beam accurately and efficiently to power reception devices without leaking of the microwave beam to the outside is required. As such techniques, a method (Japanese Patent Unexamined Publication No. 2013-236524) of inducing the moving object to a power supply position by recognizing a position of the moving object being at a power reception side is known. In addition, a method (Japanese Patent Unexamined Publication No. 2008-92703) of realizing power transmission according to a position of a power reception antenna by mechanically controlling a device of the power transmission side is known.
FIG. 11 is a diagram illustrating an example of a configuration of a power transmission system of the related art. Microwaves are supplied to power transmission antenna 103 through microwave transmission passage 102 from microwave generator 101. Microwave transmission passage 102 includes a distributor and an amplifier in some cases. Power transmission antenna 103 has a power transmission surface with a large size which can accommodate a movement range (position deviation range) of power reception antenna 105. In the power transmission surface, only a portion corresponding to a power reception surface of power reception antenna 105 is opening portion 104 of the power transmission antenna. The electromagnetic waves are radiated from opening portion 104, and the electromagnetic waves are not radiated from a portion other than opening portion 104. With this, efficient microwave transmission is realized. The electromagnetic waves received at power reception antenna 105 is properly converted into the electric power in power conversion circuit 106, and then the electric power is supplied to power supply target 107.